Equipment for winding material into core and coreless rolls is known in the art. For purposes of illustrating such prior art, one particular type of coreless plastic bag winder will be described, i.e., a winder for plastic garbage or trash bags, kitchen bags, wastebasket liners, food storage bags, etc. Further background regarding bag winders may be found in U.S. patent application Ser. No. 08/662,311, entitled Method And Apparatus For Winding Bags Onto A Spindle, Gietman et al., filed Jun. 11, 1996, which is hereby incorporated by reference.
Generally, a continuous strip of bags is fed to the winder, and the winder prepares coreless rolls therefrom. The bags themselves are produced in upstream bag making equipment or on a separate piece of equipment, from which a continuous strip of bags is produced.
In most conventional bag making equipment a tube of plastic film is extruded through an extruding die, and the tube is then flattened before it enters the bag machine. In the bag machine the film is sealed across its width to form the bottom of the finished product. The open top of the bag can be formed in different ways. For example, the bag can simply be cut. In this type of bag machine, individual bags are formed which are typically folded and placed into suitable packaging for the individual or institutional consumer. In the other type of bag machine, the top is formed by perforating the bag across its width. The bag may then be folded longitudinally, either before or after the perforation step, to provide a continuous strip of connected and folded bags. Such bags are then wound into a core or coreless roll.
One prior art winder has been sold by CMD Corporation Appleton, Wis., the assignee of the present invention. Such winder includes a dancer mechanism to sense the tension of the strip of bags being fed to the winder. The dancer mechanism includes a connection to the winder drive motor, wherein the speed of the winder can be "slaved" to the output speed of an upstream bag making equipment.
The prior art winder also includes haul-off nip rollers, to feed the strip into the winder, and an interrupt section to periodically break the perforations between certain bags in the strip. The frequency of the interruption is determined by the number of bags to be included in each roll. For example, if the roll is to contain twenty bags, the interrupt section will break every twentieth perforation.
Downstream of these sections, the prior art winder includes a turret assembly with three spindles mounted 120.degree. apart. To begin winding a roll of bags the leading end of one strip of bags is directed to a first spindle when the turret is in a transfer position. After the bag is secured to the spindle by a transfer mechanism such as that described in U.S. Pat. No. 4,667,890, incorporated herein by reference, the turret is rotated 120.degree. so that the first spindle is in a winding position and the strip is wound into a coreless roll. Following completion of the roll winding, the turret rotates again to a removal station where the roll is pushed off the first spindle by a push-off palm for subsequent packaging. When the winding of the one roll is completed the leading end of the film is directed to a second spindle in the transfer position.
A variety of prior art mechanisms are used to direct the leading end of a strip to the spindle. Generally, an airhorn and kick-roll mechanism were used to effect the transfer. The kick-roll is a pneumatic activated roller located beneath a traveling belt at the area near the transfer location. At the time of transfer, the roller would be extended by a piston rod to quickly push against the belt to "flip" the leading edge of the strip of bags up into the air above the lower belt. At the same time, an airhorn would descend around the spindle, the airhorn being a half-cylinder containing air ports on one edge. The combination was intended to direct the leading edge of the bag strip around the spindle and tuck it into its own nip to create the attachment. Another system used "fingers" that passed between the ropes and/or an air blast between the ropes carrying the film and to deflect the leading edge of the film into the airhorn (alone or in combination with the other mechanisms). Prior art air horns are shown in U.S. Pat. Nos. 5,318,237 and 5,337,698.
These systems, while being better than earlier systems, suffers from drawbacks including ineffective transfers, such as a failure of the leading edge to tuck into its own nip. This failure is caused in part by air currents in and near the air-horn, and in part by the structure used to direct the leading edge. Because of the high speeds utilized in winders if the airhorn and kick-roll system failed to properly attach the moving plastic web to the spindle, a great deal of waste would occur before the next strip would arrive at the transfer position.
One prior art design blows air directly at the film as it crests over the kick roll in an effort to direct the film into the airhorn. However if the air hits the film improperly it will blow the film back down so that it continues on away from the air horn instead of blowing it back up into the airhorn.
Another problem with the prior art is that a second row of air holes blowing air up into the air horn can cause the film to stick to the horn instead of the spindle. Yet another problem is that as the film travels around the air horn its shape did a poor job of tucking the film back in at the bottom of the spindle to cause the film to nip within itself. Other problems with prior art designs is that there were numerous critical physical orientations and distances, such as the distance from the kick roll to the spindle and/or air horn, and the angle of air to the leading edge of the film. If any of the critical parameters weren't met the winder would likely not wind properly. Thus, when servicing a winder it was often difficult to put the winder back into use (i.e. set up).
Accordingly, a winder which economically and effectively transferred a leading edge of a strip of plastic to a spindle would represent a significant advance in the art. Such a winder will preferably be easy to set up.
Prior art designs often used compressed air injected into a spindle at the unloading position to lubricate the spindle surface to make roll removal easier. (See, for example, U.S. Pat. No. 5,337,968). Another prior art feature intended to make roll removal easier is a tapered spindle. Prior art spindles often provided a large taper, such as about 0.06 in. diameter reduction per foot, in the belief that it would make removal of roll 302 easier.
Prior art spindles failed to properly account for the proper ratio of air inlet area to air outlet area of the spindle when designing the air lubricant system. For example, some prior art designs were unable to build up a sufficiently large back pressure at the face of the spindle, thus they were unable to force the roll to expand enough to float on a cushion of air. The air lubricant system typically included a plurality of air holes through which air can be selectively injected.
Accordingly, a spindle design that provides for an effective and easy removal is desirable. Such a system should have a suitable back pressure.
Roll removal is typically performed by a push-off palm (after the air lubrication is provided). A prior art push palm plate used by the assignee of this invention included a slot without contact with the spindle. The spindle can be surrounded by the palm in one quadrant, or all four quadrants. However, four quadrant palms have excessive moving parts to move into position, and are thus prone to failure. Accordingly, a push-off palm that properly pushes a roll off, without being prone to failure, is desired.